Experimental and computational studies of the influence of non-ionic surfactants with coumarin moiety as corrosion inhibitors for carbon steel in 1.0 M HCl

Electrochemical behavior and theoretical studies of arylazo (1-naphthyl-2-cyanoacetamide) derivatives as new corrosion inhibitors for Inconel 800 in chloride solution

In this study, synthesize and insight the corrosion inhibition properties of two novel derivatives of 1-naphthyl-2-cyanoacetamide (NCDs) [2-cyano-2-((5,6-dimethyl-1H-benzo[d]imidazol-2-yl) diazenyl)-N (naphthalene-1-yl)acetamide] (NCD1) and [2-Cyano-N-(naphthalene-1-yl)-2-[(4,6-dimethyl-1H-pyrazolo [3, 4-b] pyridine-3-yl) hydrazono] acetamide] (NCD2). The characterization of the synthesized NCDs was confirmed through the utilization of Mass fragmentation analysis, 1H-NMR, and IR. The corrosion inhibition performance of NCDs as a novel and environmentally safe corrosion inhibitor has been investigated by electrochemical techniques, a chemical technique, and theoretical studies for its anti-corrosion behavior of Inconel 800 in chloride medium. In addition, the surface morphology and inhibitor adsorption on the Inconel 800 surface were confirmed utilizing SEM, EDX, FTIR, and AFM. The advantages of NCDs include their low toxicity, environmental friendliness, ease of preparation, low odor, contain (N, O, and π-Bonds), and the inhibition efficiency elevated with decreasing solution temperature as well as inhibitor dose increase, yielding increased efficiencies of 91.8% and 95.7% for NCD1 and NCD2, respectively, at the optimum concentration of 21 × 10-6 mol. L-1 and 298 K temperature. An analysis of Tafel plots reveals that NCDs adhere to a mixed and isothermal Langmuir adsorption mechanism. Density Functional Theory (DFT) and Monte Carlo (MC) simulation manifest the two compounds of NCDs can be adsorbed at the Fe (110) surface in a paralleled way, and can have a smaller energy gap (ΔE) value and exhibit higher efficiency. The experimental and theoretical findings confirm that the synthesized compounds obtained are capable of protecting the Inconel 800 from corrosion by creating an anti-corrosion coating on the surface.

Exploring the synthesis, characterization, and corrosion inhibition of new tris-thiosemicarbazone derivatives for acidic steel settings using computational and experimental studies

A novel two tri-thiosemicarbazones derivatives, namely 2,2',2''-((2-Hydroxybenzene-1,3,5-triyl)tris(methanylylidene))tris(N-benzylhydrazine-1-carbothioamide) (HBC) and 2,2',2''-((2-hydroxybenzene-1,3,5-triyl) tris (methanylylidene)) tris (N-allylhydrazine-1-carbothioamide) (HAC), have been synthesized and their chemical structures were determined using different spectroscopic and analytical approaches. Then, utilizing methods including open circuit potential, potentiodynamic polarization, and electrochemical impedance spectroscopy, the inhibitory effect of the synthesized thiosemicarbazones on mild steel (MS) in an acidic environment (0.5 M H2SO4) was thoroughly investigated. Remarkably, raising the concentration of our recently synthesized tri-thiosemicarbazones HBC and HAC increased the inhibitory efficiency values. The η values of the two investigated tri-thiosemicarbazones derivatives (HAC and HBC), at each concentration are extremely high, and the maximum values of the efficiencies are 98.5% with HAC and 98.8% with HBC at the 800 ppm. The inhibitors adsorbed on the mild steel surface and generated a charge and mass movement barrier that protected the metal from hostile ions. According to polarization curves, HBC and HAC act as mixed-type inhibitors. Electrochemical impedance testing revealed a notable rise in charge transfer resistance (Rct) readings to 4930-Ω cm2, alongside a reduction in the Constant Phase Element (CPE) value to 5.81 μF, suggesting increased effectiveness in preventing corrosion. Also, density functional theory (DFT) was applied to investigate the assembled tri-thiosemicarbazones HBC and HAC. Moreover, the adsorption mechanism of HBC and HAC on the mild steel surface was explored using Monte Carlo simulation. Finally, the theoretical outputs were discovered to support the practical outcomes.

An Exploratory Experimental Analysis Backed by Quantum Mechanical Modeling, Spectroscopic, and Surface Study for C-Steel Surface in the Presence of Hydrazone-Based Schiff Bases to Fix Corrosion Defects in Acidic Media

This work focuses on developing corrosion control and protecting the environment by creating affordable, sustainable, environmentally friendly, and efficient corrosion resistance chemicals. That is, through synthesized three hydrazone Schiff bases E-2-(1-hydrazonoethyl)thiazole (HTZ), 2-((E)-(((Z)-1-(thiazol-2-yl)ethylidene)hydrazono)methyl)phenol (HTZS), and 2-((E)-(((Z)-1-(pyridin-2-yl)ethylidene)hydrazono)methyl)phenol (HPYS) and corrosion inhibitors for C-steel in 8 M H3PO4 solution that were studied. The chemicals were analyzed by using 1H NMR and 13C NMR spectroscopy to learn more about them. Predominantly, the hydrazone-based Schiff bases have been considered powerful inhibitors due to their ability to be adsorbed with very low concentrations through their reactive sites (N, O, and S). Maximum surface (θmax) coverage and inhibition efficiency of 83.33% were sufficiently found at 99.00 × 10-3 mol/L concentration of HTZS at 293 K. Galvanostatic experiments demonstrated that raising the concentration of hydrazones improved mass transfer resistance. To study microstructure, scanning, reflectance, and energy-dispersive X-rays were used. Roughness and qualitative adhesion of the adsorbed layer were estimated by an atomic force microscope. After adding 99.00 × 10-3 mol/L of HTZS, the degree of surface brightness and reflectance increases to 137.20, relative to the corroded electrolyte-free solution 27.70. The roughness (Ra) decreased from 0.468 to 0.088 μm by adding HTZS. A surface morphology study confirmed that adding hydrazones to the C-steel dissolution bath greatly improves the surface's look and texture quality. The atomic absorption spectroscopy technique was used to compare the concentration of the iron ions that remained in the solution after galvanostatic analysis in the absence and presence of the hydrazones under different conditions; it was found that the inhibited solution contained lower concentrations of iron ions as compared to the uninhibited solution. The DFT theoretical analysis verified the observation of hydrazone physical adsorption through bonding electrons that obey kinetic adsorption isotherms. It is based on examining the highest occupied molecular orbital-lowest occupied molecular orbital (HOMO-LUMO), the Fukui functions, and the Mulliken atomic charge. Overall, the results suggest that HTZS is a good corrosion inhibitor with a large surface area due to the presence of S, N, and O atoms, allowing for creating a larger surface due to the large molecular volume of atoms protecting against the corrosion process.

Electrochemical and DFT Studies of the Pistacia Integerrima Gall Extract: An Eco-friendly Approach towards the Corrosion of Steel in Acidic Medium

A novel application of the Pistacia integerrima gall extract as an environmentally friendly corrosion inhibitor is reported in this study. The major phytochemicals present in the gall extract, namely pistagremic acid, β-sitosterol, pistiphloroglucinyl ether, pistaciaphenyl ester, naringenin, and 5,7-dihydroxy-2-(4-hydroxyphenyl)-2,3-dihydrochromen-4-one, play key roles in its anticorrosive behavior on steel in aggressive media. Several approaches were used to study the corrosion prevention activity of steel in 1 M H2SO4, including weight loss analysis, scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), and density functional theory (DFT). At 2000 mg L-1, the highest efficiency of 92.19% was observed in 1 M H2SO4. An SEM study was conducted to validate the surface coverage of the metal surface. DFT studies revealed several nucleophilic regions present in the phytochemicals of the inhibitor, which supported the favorable nucleophilicity. Corrosion studies have not been performed on this sample. Phytochemicals make it an effective corrosion inhibitor, and its extraction process utilizes distilled water, making it better than other inhibitors. It has been proven that the obtained values of ΔEInhDFT for pistiphloroglucinyl, pistaciaphenyl ether, and naringenin organic compounds were very low, confirming the high reactivity of these corrosion inhibitors. The order of the values of ΔEInhDFT is as follows: pistaciaphenyl ether > pistiphloroglucinyl ether > naringenin organic compound; this suggests that pistaciaphenyl ether is more reactive than the other compounds. In this study, P. integerrima gall extract emerges as a novel and highly effective corrosion resistance agent in 1 M H2SO4, chosen for its relevance to acid pickling and cleaning processes.

Surfactants as biodegradable sustainable inhibitors for corrosion control in diverse media and conditions: A comprehensive review

BACKGROUND

Corrosion is a challenging and potentially harmful process that involves the continuing, impulsive deterioration of metallic structures via reactions involving environmental components and electro- or chemical processes. To inhibit corrosion, various additives are added. Traditional additives, on the other hand, contain environmentally hazardous substances. Surfactants are less expensive, easier to manufacture, and have high inhibitory efficacy and low toxicity compared to standard corrosion inhibitors. They are often employed as corrosion inhibitors to protect metallic materials against corrosion.

METHODS

Surfactant molecules' amphiphilic nature promotes adsorption at surfaces such as the metal/metal oxide-water interface. Surfactant adsorption on metals and metal oxides forms a barrier that can prevent corrosion.

SIGNIFICANT FINDINGS

This review of surfactants as corrosion inhibitors aims to offer a systemic evaluation of various surfactant physical and chemical properties, surfactant influence in corrosion inhibition, and surfactant used in corrosion inhibition that can be used to enhance the efficacy of surfactant use as corrosion inhibitors in a variety of environments. The effect of several parameters on the potential to suppress corrosion of surfactant molecule series is also discussed here.

Electrochemical and DFT studies of Terminalia bellerica fruit extract as an eco-friendly inhibitor for the corrosion of steel

It is well known that metal corrosion causes serious economy losses worldwide. One of the most effective ways to prevent corrosion is the continuous development of high-efficient and environment-friendly corrosion inhibitors. Among the widely used organic and inorganic corrosion inhibitors, plant extracts are top candidates due to their nontoxic nature. The present study reports a novel application of the methanolic extract of Terminalia bellerica fruits as an environment friendly corrosion inhibitor for steel in sulphuric acid medium. The phytochemicals of the extract, namely Ellagic, Gallic, and Malic acids, play a key role of the anti-corrosive behavior of the extract. The corrosion prevention activity was studied on the steel in 1 M H2SO4 using a variety of approaches including weight loss analysis (WL), scanning electron microscope (SEM), electrochemical impedance spectroscopy (EIS), density functional theory (DFT), natural bond orbital analysis (NBO), Fukui function and Monte Carlo simulations (MC). In 1 M H2SO4 solution, the maximum electrochemical inhibition efficiency of 91.79% was observed at 4000 mg/L concentration of the extract. The NBO analysis showed that the charge density of the double bonds and the oxygen atoms of carbonyl and hydroxyl groups of the phytochemicals lies on the top of the natural bond orbitals which promotes the anticorrosive properties of the investigated inhibitors. The surface coverage of steel was validated by SEM measurements. According to DFT studies, numerous nucleophilic regions were present in the active phytochemical constituents of the inhibitor, demonstrating their favorable nucleophilicity. The computed electronic structure of the phytochemicals revealed band gaps of 4.813, 5.444, and 7.562 eV for Ellagic, Gallic, and Malic acids respectively suggesting effective metal-inhibitor interactions. A good correlation between experimental and theoretical findings was addressed.

Experimental and theoretical investigations of the effect of bis-phenylurea-based aliphatic amine derivative as an efficient green corrosion inhibitor for carbon steel in HCl solution

A novel bis-phenylurea-based aliphatic amine (BPUA) was prepared via a facile synthetic route, and evaluated as a potential green organic corrosion inhibitor for carbon steel in 1.0 M HCl solutions. NMR spectroscopy experiments confirmed the preparation of the targeted structure. The corrosion inhibitory behavior of the prospective green compound was explored experimentally by electrochemical methods and theoretically by DFT-based quantum chemical calculations. Obtained results revealed an outstanding performance of BPUA, with efficiency of 95.1% at the inhibitor concentration of 50 mg L-1 at 25 °C. The novel compound has improved the steel resistivity and noticeably reduced the corrosion rate from 33 to 1.7 mils per year. Furthermore, the adsorption study elucidates that the mechanism of the corrosion inhibition activity obeys Langmuir isotherm with mixed physisorption/chemisorption modes for BPUA derivatives on the steel surface. Calculated Gibb's free energy of the adsorption process ranges from -35 to -37 kJ mol-1. The SEM morphology analysis validates the electrochemical measurements and substantiates the corrosion-inhibiting properties of BPUA. Additionally, the eco-toxicity assessment on human epithelial MCF-10A cells proved the environmental friendliness of the BPUA derivatives. Density functional theory (DFT) calculations correlated the inhibitor's chemical structure with the corresponding inhibitory behavior. Quantum descriptors disclosed the potentiality of BPUA adsorption onto the surface through the heteroatom-based functional groups and aromatic rings.

Synthesis and applications of novel Schiff base derivatives as corrosion inhibitors and additives for improvement of reinforced concrete

The studied Schiff-base compounds in this work are multitasked investigated as corrosion inhibitors and also, to improve the physical and mechanical properties of reinforced concrete. The efficiency inhibition of the two novel Schiff-base compounds named (DHSiMF) and (DHSiB) for corrosion of carbon-steel in aqueous media of 1 M HCl was assessed via electrochemical methods and loss in weight. FT-IR, 1H-NMR spectra and elemental analysis were used to confirm the structure of such compounds. It was found to have successful inhibition even at low concentrations in tested media, as an increase in inhibitor concentration led to an improvement in the inhibition efficiency. The weight loss results clearly demonstrate that DHSiMF of C-steel in 1 M HCl has a higher inhibition efficiency than DHSiB, with a maximum inhibition efficiency (85%) attained at 1 × 10-2 M from DHSiMF. Electrochemical experiments likewise revealed the same order, but with a maximal inhibitory efficiency of 98.1%. The addition of inhibitors to the corrosive media dramatically changed the anodic Tafel constants (βa) and cathodic Tafel constants (βc), indicating a mixed type nature. Electrochemical polarization curves illustrated the functions of mixed-type inhibition and the action of adsorption matching with the Langmuir adsorption isotherm. The ∆Gads values for DHSiMF and DHSiB at temperatures (ranging from 303 to 333 K) are - 34.42 kilojoule/mole to - 37.51 kilojoule/mole. These values indicate that the compounds' adsorption types are chemo-physical adsorption. X-ray diffraction (XRD) and Scanning electron microscopy (SEM) experiments were used to check the existence of the protection layer on the surface of carbon steel by analyzing the morphologies of the corrosion effects and the formed chemical compositions of the corrosion outcomes. For the concrete, the findings suggest that the chemical reaction that takes place between the DHSiMF and DHSiB and the concrete mix will result in an increase in the flexural strength, the compressive strength, and the indirect tensile strength of the concrete that is made of the gravel and dolomite aggregate.

PickT: A Decision-Making Tool for the Optimal Pickling Process Operation

This research approaches knowledge gaps related to the pickling process dynamic modelling (the lack of predictability and simplicity of existing models) and answers the practical need for a software tool to facilitate the optimum process operation (by delivering estimations of the optimum corrosion inhibitor addition, optimum pickling bath lifetime, corrosion rate dynamic evolution, and material mass loss). A decision-making tool, PickT, has been developed and verified with the help of measurements from two different pickling experiments, both involving steel in hydrochloric acid. The first round of experiments lasted 336 h (each pickling batch duration was 24 h) and Cetilpyridinium bromide (CPB) was the corrosion inhibitor in additions from 8% to 12%. The collected dataset served for the tool development and first verification. The second round of experiments lasted 10 h (each batch duration was 2 h) and involved metformin hydrochloride (MET) in additions between 3.3 g/L and 10 g/L. This dataset served to test the transferability of PickT to other operating conditions in terms of corrosion inhibitor type, additions, batch duration and pickling bath lifetime magnitude. In both cases PickT results are in accordance with experimental findings. The tool advantages consist of the straightforward applicability, the low amount of field data required for reliable forecasts and the accessibility for untrained professionals from the industry.

Polymeric surfactants as ideal substitutes for sustainable corrosion protection: A perspective on colloidal and interface properties

Surfactants are well known for their colloidal and corrosion inhibition potential (CIP) due to their strong propensity to interact with metallic surfaces. However, because of their small molecular size and the fact that they are only effective at relatively high concentrations, their application in aqueous phase corrosion inhibition is often restricted. Polymeric surfactants, a unique class of corrosion inhibitors, hold the potential to eradicate the challenges associated with using surfactants in corrosion inhibition. They strongly bond with the metallic surface and offer superior CIP because of their macromolecular polymeric structure and abundance of polar functional groups. In contrast to conventional polymeric corrosion inhibitors, the inclusion of polar functional groups also aids in their solubilization in the majority of popular industry-based electrolytes. Some of the major functional groups present in polymeric surfactants used in corrosion mitigation include O (ether), glycidyl (cyclic ether), -CONH2 (amide), -COOR (ester), -SO3H (sulfonic acid), -COOH (carboxyl), -NH2 (amino), - + NR3/- + NHR2/- + NH2R/- + NH3 (quaternary ammonium), -OH (hydroxyl), -CH2OH (hydroxymethyl), etc. The current viewpoint offers state-of-the-art information on polymer surfactants as newly developing ideal alternatives for conventional corrosion inhibitors. The industrial scale-up, colloidal, coordination, adsorption properties, and structural requirements of polymer surfactants have also been established based on the knowledge obtained from the literature. Finally, the challenges, drawbacks, and potential benefits of using polymer surfactants have also been discussed.

Insight into the corrosion mitigation performance of three novel benzimidazole derivatives of amino acids for carbon steel (X56) in 1 M HCl solution

Three new organic molecules having a benzimidazole base were synthesized and used for the protection of carbon steel (X56) against corrosion in 1.00 M HCl solution. The protection against corrosion was assessed by electrochemical frequency modulation (EFM), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP). In addition, the electronic and molecular structure of the synthesized molecules were computationally investigated and correlated to corrosion inhibition. Global reactivity descriptors, molecular orbitals (FMO and NBO) and local reactivity descriptors (molecular electrostatic potential map and Fukui functions) were discussed. The results showed a maximum protective efficiency range between 95% and 98% indicating high corrosion inhibition. Moreover, all molecules were able to combat the cathodic as well as anodic reaction simultaneously, revealing a mixed-type resistance. SEM and EDX verified effective adhering film formation to the metal surface. In accordance, the theoretical calculations showed effective electron reallocation from the organic film to the X56 c-steel surface. Furthermore, the adsorption annealing calculations revealed that structural layers of these molecules hold parallel and close to the metal surface with adsorption energy from 249.383 to 380.794 kcal mol^-1, showing strong inhibitor-metal contact.

Coco Monoethanolamide Surfactant as a Sustainable Corrosion Inhibitor for Mild Steel: Theoretical and Experimental Investigations

Recent studies indicate that surfactants are a relatively new and effective class of corrosion inhibitors that almost entirely meet the criteria for a chemical to be used as an aqueous phase corrosion inhibitor. They possess the ideal hydrophilicity to hydrophobicity ratio, which is crucial for effective interfacial interactions. In this study, a coconut-based non-ionic surfactant, namely, coco monoethanolamide (CMEA), was investigated for corrosion inhibition behaviour against mild steel (MS) in 1 M HCl employing the experimental and computational techniques. The surface morphology was studied employing the scanning electron microscope (SEM), atomic force microscope (AFM), and contact measurements. The critical micelle concentration (CMC) was evaluated to be 0.556 mM and the surface tension corresponding to the CMC was 65.28 mN/m. CMEA manifests the best inhibition efficiency (η%) of 99.01% at 0.6163 mM (at 60 °C). CMEA performs as a mixed-type inhibitor and its adsorption at the MS/1 M HCl interface followed the Langmuir isotherm. The theoretical findings from density functional theory (DFT), Monte Carlo (MC), and molecular dynamics (MD) simulations accorded with the experimental findings. The MC simulation's assessment of CMEA's high adsorption energy (-185 Kcal/mol) proved that the CMEA efficiently and spontaneously adsorbs at the interface.

Preparation of zwitterionic ionic surfactants-based sulphonyl for steel protections: Experimental and theoretical insights

Designating an organic inhibitor with a specific chemical structure that actively participates in steel protection by increasing adsorption on the steel surface. Based on that, we synthesized three zwitterionic surfactants based on azomethine with different hydrophobic chain lengths labeled ZWSO, ZWSD, and ZWSH. The presence of azomethine group, electrons, and heteroatoms in the zwitterionic surfactant’s amphipathic structure helped to improve C-steel protection. Their inhibitory activity toward steel corrosion was investigated utilizing electrochemical impedance spectroscopy (EIS), gravimetrical, and potentiodynamic polarization techniques. Importantly, the surfactant tail influenced corrosion inhibition performance; as surfactant tail length increased, so did inhibition efficiency due to increased adsorption affinity. The inhibition efficiencies of ZWSO, ZWSD, and ZWSH are 87.15, 89.82, and 91.36%, respectively. Tafel data clarified that ZWSO, ZWSD, and ZWSH inhibitors behave as mixed-type inhibitors following the modified Langmuir isotherm. The inhibitors can adsorb physiochemically on the steel surface with ∆G ads ranges from −38.48 to −44.6 kJ mol−1. The SEM confirms that the morphology of C-steel becomes smoother because of inhibitor adsorption. The DFT and MCs output data supported the experimental performance of the tested ZWSO, ZWSD, and ZWSH inhibitors and especially their dependence on surfactant tail length.

A Review on Interactions between Amino Acids and Surfactants as Well as Their Impact on Corrosion Inhibition

Amino acid-surfactant interactions are central to numerous studies because of their increased effectiveness in chemical, biological, household and industrial use. This review will focus on the impact and effect of the physicochemical properties, temperature, pH, and surfactant chain length of the amino acid for detailed exploration of amino acids and surfactants in aqueous medium. The impact of cosolvent on self-aggregation, critical micelle concentration (CMC), and binding affinity with other biomolecules, as well as amino acid-surfactant interactions, are the epicenters. The results show that increasing the temperature causes negative enthalpy for ionic surfactants and micellization, implying that micellization and amino acids are thermodynamically spontaneous and exothermic, accompanied by positive entropy. As these physicochemical studies are additive, the amino acid and ionic surfactant interactions provide clues on protein unfolding and denaturation under different media, which further changes with a change in physiological conditions like pH, cosolvent, chain length, and temperature. On varying the pH, the net charge of the amino acid also changes and, subsequently, the binding efficiency of the amino acids to the surfactants. The presence of cosolvent causes a lowering in the hydrophobic chain, which changes the surfactant's CMC. At a reduced CMC, the hydrophobic characteristic of amino acid-surfactant associations is amplified, leading to rapid denaturation of proteins that act as propulsion under the influence of extended chain surfactants. Amino acids are one of the most intriguing classes of chemicals that produce high inhibitory efficacy. Amino acids are also a component of proteins and therefore, found in a significant part of the human body, further making them a promising candidate as corrosion inhibitors. In this review article, authors have also focused on the collection and investigation for application of amino acid-surfactant interactions in corrosion inhibition. Various predictive studies/in silico studies are also reported by many research groups, such as density functional theory (DFT) calculations and molecular dynamics simulations to obtain tentative electronic, structural, and physiochemical characteristics like energies of the highest occupied molecular orbitals and lowest unoccupied molecular orbitals, binding energy, Gibb's free energy, electronegativity, polarizability, and entropy. In silico studies are helpful for the mechanism predictions of the process occurring on metal surfaces.

Ethyl ester/acyl hydrazide-based aromatic sulfonamides: facile synthesis, structural characterization, electrochemical measurements and theoretical studies as effective corrosion inhibitors for mild steel in 1.0 M HCl

In this research paper, aromatic sulfonamide-derived ethyl ester (p-TSAE) and its acyl hydrazide (p-TSAH) were directly synthesized, characterized, and employed for the first time as prospective anticorrosive agents to protect mild steel in 1.0 M HCl conditions. The corrosion efficiency was probed by electrochemical methods including polarization, impedance, and frequency modulation measurements. Optimal efficiencies of 94% and 92% were detected for the hydrazide and ester, respectively, revealing excellent corrosion inhibition. Moreover, both the hydrazide and ester molecules combat the cathodic and anodic reactions correspondingly in a mixed-type manner. The electron transfer (ET) at the inhibitor/metal interface was evaluated using DFT at the B3LYP/6-31g(d,p) level. Natural bond orbital analysis (NBO) and frontier molecular orbital analysis (FMO) calculations showed superior capabilities of the synthesized inhibitors to easily reallocate charge into the metal surface. However, the hydrazide molecules showed slightly better inhibition efficiency than the ester due to the strong interaction between the lone pairs of the nitrogen atoms and the d-orbitals of the metal. The chemical hardness of the hydrazide and ester are 2.507 and 2.511 eV, respectively, in good accordance with the recorded electrochemical inhibition efficiencies for both molecules. Good and straightforward correlations between the experiments and calculations are obtained.

Insights into the adsorption and corrosion inhibition properties of newly synthesized diazinyl derivatives for mild steel in hydrochloric acid: synthesis, electrochemical, SRB biological resistivity and quantum chemical calculations

Two azo derivatives, 4-((4-hydroxy-3-((4-oxo-2-thioxothiazolidin-5-ylidene)methyl)phenyl) diazinyl) benzenesulfonic acid (TODB) and 4-((3-((4,4-dimethyl-2,6-dioxocyclohexylidene) methyl)-4-hydroxyphenyl)diazinyl) benzenesulfonic acid (DODB) were synthesized and characterized using Fourier-transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (1H-NMR) and mass spectral studies. Gravimetric methods, potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), electrochemical frequency modulation (EFM) techniques and inductive coupled plasma-optical emission spectroscopy were used to verify the above two compounds' ability to operate as mild steel (MS) corrosion inhibitors in 1 M HCl. Tafel data suggest that TODB and DODB have mixed-type characteristics, and EIS findings demonstrate that increasing their concentration not only alters the charge transfer (R ct) of mild steel from 6.88 Ω cm2 to 112.9 Ω cm2 but also changes the capacitance of the adsorbed double layer (C dl) from 225.36 to 348.36 μF cm-2. At 7.5 × 10-4 M concentration, the azo derivatives showed the highest corrosion inhibition of 94.9% and 93.6%. The inhibitory molecule adsorption on the metal substrate followed the Langmuir isotherm. The thermodynamic activation functions of the dissolution process were also calculated as a function of inhibitor concentration. UV-vis, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX) techniques were used to confirm the adsorption phenomenon. The quantum chemical parameters, inductively coupled plasma atomic emission spectroscopy (ICPE) measurements, and the anti-bacterial effect of these new derivatives against sulfate-reducing bacteria (SRB) were also investigated. Taken together, the acquired results demonstrate that these compounds can create an appropriate preventing surface and regulate the corrosion rate.

Synthesis, Characterization, Thermodynamic Analysis and Quantum Chemical Approach of Branched N, N′-bis(p-hydroxybenzoyl)-Based Propanediamine and Triethylenetetramine for Carbon Steel Corrosion Inhibition in Hydrochloric Acid Medium

The influence of branched N, N′-bis(p-hydroxybenzoyl) containing propylenediamine (PDA) and triethylenetetramine (TETA) composites for corrosion inhibition of carbon steel in acidic solution (1 M HCl) was investigated using several quantum chemical, electrochemical impedance spectroscopy and potentiodynamic polarization as electrochemical techniques. The investigated molecules were posteriorly characterized by proton nuclear magnetic resonance (1H NMR) and Fourier transform infrared spectroscopy (FTIR) while the surfaces of carbon steel test coupons were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The obtained results revealed that the two amino compounds, N, N′-bis(p-hydroxybenzoyl) propanediamine (N, N′-HBPDA) and N, N′-bis(p-hydroxybenzoyl) triethylenetetramine (N, N′-HBTETA), have significant efficiency toward steel corrosion attack and its inhibition performance was significantly boosted by increasing concentration of di- and tetramine containing inhibitors. The two inhibitors achieved a maximum corrosion inhibition efficiency of 99.1% as indicated from polarization measurements. The isotherm feature of Langmuir adsorption appeared to be proper factor for associating the experimental gains with an applicable mechanism of inhibition process. The free energy ∆Gads was calculated to be − 27.5, 29.1 kJ/mol based on the adsorption isotherm model, indicating physical adsorption on the carbon steel surface. Further, images of the morphological analysis exhibited various features of attack owing to the aggressive medium and the employed concentration of the inhibitor. These synthesized amines supplied many favorable scores in the fabrication of functional mixed-type inhibitors. The computational studies reveal that N, N′-HBPDA and N, N′-HBTETA molecules could absorb via several lone pairs and π clouds, confirming their ability to be good corrosion inhibitors.

Surface protection against corrosion of Ni turbine blades by electrophoretic deposition of MnO2, TiO2 and TiO2-C nanocoating

The turbine blades of turbochargers are corroded after being cleaned with water in the presence of gasses produced during the combustion of heavy fuel. For that, manganese oxide (MnO2), titanium dioxide (TiO2), and titanium oxide-graphene (TiO2-C) nanomaterials have been coated on the nickel alloy, which is the composition of turbine blades, by the electrophoretic deposition technique for protection against the corrosion process. The anticorrosion performance of nanomaterial coatings has been investigated using electrochemical methods such as open circuit potential, potentiodynamic, electrochemical impedance, and linear polarization resistance in a 1 M H2SO4 solution saturated with carbon dioxide. The corrosion rate of nanomaterial-coated Ni-alloy was lower than bare alloy, and potential corrosion increased from -0.486 V for uncoated Ni-alloy to -0.252 V versus saturated calomel electrode for nanomaterial coated Ni-alloy electrodes. Electrochemical measurements show that TiO2 coated Ni-alloy corrosion has good protective qualities, with an efficiency of 99.91% at 0.146 mA cm2 current density in sulfuric acid media. The findings of this study clearly show that TiO2 has a high potential to prevent nickel alloy turbine blades from corrosion in acidic media. Furthermore, the surface morphologies have revealed that TiO2 and MnO2 coatings might successfully block an acid assault due to the high adhesion of the protective layer on the nickel alloy surface. The use of X-ray diffraction (XRD) enhanced the various measures used to determine and study the composition of the alloy surface's protective coating.

Effective corrosion inhibition of mild steel in hydrochloric acid by newly synthesized Schiff base nano Co(ii) and Cr(iii) complexes: spectral, thermal, electrochemical and DFT (FMO, NBO) studies

Two new cobalt(ii) and chromium(iii) complexes were synthesized and characterized by FT-IR, 1HNMR, UV, elemental analysis, TGA, conductivity, XRD, SEM, and magnetic susceptibility measurements. Structural analysis revealed a bi-dentate chelation and octahedral geometry for the synthesized complexes. The optical band gap of the Co(ii)-L and Cr(iii)-L complexes was found to be 3.00 and 3.25 eV, respectively revealing semiconducting properties. The X-ray diffraction patterns showed nano-crystalline particles for the obtained complexes. In addition, the synthesized metal complexes were examined as corrosion inhibitors for mild steel in HCl solution. The electrochemical investigations showed a maximum inhibition efficiency of 96.60% for Co(ii)-L and 95.45% for Cr(iii)-L where both complexes acted as mixed-type inhibitors. Frontier Molecular orbital (FMO) and Natural bond orbital (NBO) computations showed good tendency of the ligand to donate electrons to the metal through nitrogen atoms while the resultant complexes tended to donate electrons to mild steel more effectively through oxygen atoms and phenyl groups. A comparison between experimental and theoretical findings was considered through the discussion.

Corrosion mitigation for steel in acid environment using novel p-phenylenediamine and benzidine coumarin derivatives: synthesis, electrochemical, computational and SRB biological resistivity

Three novel p-phenylenediamine and benzidine coumarin derivatives were synthetized, namely: 4,4'-((((1,4-phenylenebis(azaneylylidene))bis(ethan-1-yl-1-ylidene))bis(2-oxo-2H-chromene-3,6-diyl))bis(diazene-2,1-diyl))dibenzenesulfonic acid (PhODB), 4,4'-(((-([1,1'-biphenyl]-4,4'-diylbis(azaneylylidene))bis(ethan-1-yl-1-ylidene))bis(2-oxo-2H-chromene-3,6-diyl))bis(diazene-2,1-diyl))dibenzenesulfonic acid (BODB) and 4,4'-(((-((3,3'-dimethoxy-[1,1'-biphenyl]-4,4'-diyl)bis(azaneylylidene))bis(ethan-1-yl-1-ylidene))bis(2-oxo-2H-chromene-3,6-iyl))bis(diazene-2,1-diyl))dibenzenesulfonic acid (DODB). Their chemical structures were proved by performing Fourier-transform infrared spectroscopy, proton nuclear magnetic resonance and mass spectrometry analysis. The synthesized p-phenylenediamine and benzidine coumarin derivatives were tested as corrosion inhibitors for mild steel (MS) in 1 M HCl solution using weight loss, electrochemical, morphological, and theoretical studies. The compound 3,3'-dimethoxy benzidine coumarin derivative (DODB) was proved to give the highest efficiency with 94.98% obtained from weight loss measurements. These compounds are mixed inhibitors, as seen by the polarization curves. Impedance diagrams showed that when the concentration of these derivatives rose, the double-layer capacitance fell and the charge transfer resistance increased. Calculated thermodynamic parameters were computed and the mechanism of adsorption was also studied for the synthesized p-phenylenediamine and benzidine coumarin derivatives. The ability of the synthesized derivatives to protect the surface against corrosion was investigated by scanning electron microscope (SEM), UV-visible spectroscopy and energy dispersive X-ray spectroscopy (EDX). Theoretical chemical calculations (DFT) and biological resistivity (SRB) were investigated.

Study of the Corrosion of Nickel-Chromium Alloy in an Acidic Solution Protected by Nickel Nanoparticles

This study uses nickel nanoparticles coated on the nickel-chromium (Ni-Cr) alloy by the electrodeposition technique to protect the alloy against corrosion. An open-circuit potential and potentiodynamic and linear polarization resistance in a 1 M H₂SO₄ solution saturated with carbon dioxide were used to study the anticorrosion performance of nanoparticle coatings. When coated with nanomaterials, the corrosion rate of Ni-Cr alloy was lower than when it was bare, and the potential for corrosion increased from -0.433 V for uncoated Ni-Cr alloy to -0.103 V when the electrodes were exposed to saturated calomel. Electrochemical experiments show that nickel-coated Ni-Cr alloy corrosion in sulfuric acid media has high protective characteristics, with an efficiency of 83.69% at 0.165 mA/cm² current density when pH = 1 is used. As demonstrated by the results of this research, the nickel-chromium alloy can be protected from corrosion in acidic media by a low-acidity bath coating layer. Surface morphologies have shown that coatings at different acidic scales may be able to resist an acid attack because of their excellent adherence to the nickel-chromium alloy surface. Measures for determining and studying the composition of the alloy surface's protective covering were improved using X-ray diffraction (XRD).

Anticorrosion Study for Brass Alloys in Heat Exchangers during Acid Cleaning Using Novel Gemini Surfactants Based on Benzalkonium Tetrafluoroborate

For a variety of applications, the brass alloy has been utilized to replace titanium tubes in heat exchangers. Copper alloys' high corrosion rate during the acid cleaning procedure remains a significant concern. To inhibit the corrosion of brass alloys, we prepared two novel gemini surfactants (GSs), N ₁,N ₃-dibenzyl-N ₁,N ₁,N ₃,N ₃-tetramethylpropane-1,3-diaminium tetrafluoroborate (I H) and N ₁,N ₁,N ₃,N ₃-tetramethyl-N ₁,N ₃-bis (4-methyl benzyl) propane-1,3-diaminium tetrafluoroborate (I Me), and they were characterized using Fourier transform infrared spectroscopy and ¹H nuclear magnetic resonance spectroscopy. Their inhibition performance against corrosion of brass alloys in 1 M HCl was studied using electrochemical techniques including potentiodynamic polarization (PP), electrochemical impedance spectroscopy, and electrochemical frequency modulation. The inhibition effect of the synthesized compounds was high, and it increased as the inhibitor's concentration was increased. The maximum level of inhibition efficiency was achieved at an inhibitor concentration of 100 ppm, reaching 96.42% according to PP measurements. From Langmuir data, the mechanisms of adsorption of the two GSs on the surface of copper was found to be physisorption and chemisorption adsorption. X-ray photoelectron spectroscopy and scanning electron microscopy show that the addition of the two compounds lowers the dissolution of brass ions in the corrosive solution and forms a protective layer on the surface of the brass.